Effect coating material and effect coating system, especially for vehicle bodies, using liquid-crystalline interference pigments

ABSTRACT

The present invention discloses coated objects, such as car bodies, as well as coatings for coating such objects. In order to achieve new, hitherto unknown color effects with said coatings, at least some, and preferably only platelet-like interference pigments are mixed into the coating. When the coating is applied, the interference pigments automatically align themselves in a direction approximately parallel to the object surface. These interference pigments are made of liquid crystalline side chain polymers with a nematic and a chiral component, in which the side group mesogens are at least approximately nematic, smectic and/or cholesteric. Particularly intensive tones having a hitherto unknown brilliance may thus be obtained on a coated object, or a shimmering effect depending on the angle of incidence of light and viewing direction.

BACKGROUND OF THE INVENTION

The invention relates to interference pigments based onliquid-crystalline polymers. This invention also relates to an effectcoating material and to commodity articles, especially motor vehiclebodies, which are painted therewith. Moreover, the invention comprises aprocess for the preparation of the interference pigments.Liquid-crystalline polymers are already known, for example, from DE 4008 076 A, EP 66 137 A and U.S. Pat. No. 5,188,760.

The customary automotive solid-colour paints generally involve,incorporated into a clear vehicle comprising synthetic resin, colourpigments which determine the desired coloration of the paint. The coloureffect of these pigments is based on a spectrally selective absorptioneffect, so that a spectrally broad fraction of theincident--white--light is absorbed by the pigments and only a spectrallynarrow fraction is reflected.

In the effort for brighter perceived colours, especially for vehiclebodies, the so-called effect finishes have been developed. In the caseof one group thereof, the metallic paints, small metal flakes, interalia, as pigments are incorporated by mixing into the paint vehicle. Inthe case of another group, coated mica particles are used as pigments.With these effect finishes it is possible to achieve a better brightnessof colour than with the solid-colour paints; moreover, depending on thedirection of incidence of light and/or direction of viewing, there is aslightly altered perceived colour, which is desirable. EP 383 376 A1describes such an effect finish, in which small mica flakes are coateduniformly on all sides with a crosslinked, liquid-crystalline polymer(LCP) in chiral nematic arrangement. The coloured appearance of suchpigments comes about by means of an interference phenomenon. The onlylight waves of the incident light which are reflected are those whosewavelength interferes with the equidistant interplanar spacings of theliquid-crystalline polymers, whereas the light fractions of otherwavelengths pass through the transparent body of the paint and areabsorbed by the--preferably--dark substrate. Plateletlike interferencepigments of this kind, aligned parallel to the painted surface, have adefined first colour--base colour--when viewed orthogonally and asecond, shorter-wave colour when viewed from an inclined direction. Thisviewing angle-dependent coloured appearance of the painted surface makesthe coating system highly effective, and, for specific applications inwhich such colour effects are perceived positively by the customer,highly desirable. A disadvantage is the complex preparation of theinterference pigments, making the effect coating material and,correspondingly, the effect finish on the commodity article very costly.

The preparation of interference pigments based on polysiloxanes hasbecome known, confidentially, to the Applicant, these pigments eachconsisting wholly of small fragments of a thin crosslinked film ofliquid-crystalline polymer. These interference pigments are colourlessand transparently see-through. The colour effect which can be achievedwith them is based on the regular structure and on the uniformarrangement of the molecules in the form of a liquid crystal and on theinterference, which can be traced back thereto, of a certain spectrallight fraction for which the pigment has a reflective action. The otherlight fractions pass through the pigment. By this means it is possibleto achieve stunning colour effects of different kinds, depending on theconfiguration of the coating system and/or on the interference pigmentsand mixing thereof. Aside from the novel aesthetic colour effect of thecoating system and of the coating material used therefor, this coatingsystem also offers a series of technical advantages. Owing to theirchemical composition, the interference pigments have a specific weightwhich is approximately equal to that of the vehicle of the pigmentsand/or the paint base. Therefore, there is no mass-related separation ofpigments and paint base during the storage of the coating material orduring its application by spraying using a high-speed rotating bell, asis observed in the case of conventional painting materials containingabsorption pigments--most based on metal--having high specific weights.Since, moreover, the entire colour spectrum can be produced by mixingjust a few types of interference pigments in different ratios at thepainting plant, stockkeeping on site can be limited to a few basic typesof paints, thereby simplifying very considerably the logistics relativeto the various paint colours. The interference pigments of the typediscussed are obtained by knife-coating the liquid-crystalline polymersfrom the liquid state onto a smooth substrate, for example on to apolished roller, thereby forming a thin film. As a result of theknife-coating procedure there is an alignment of the molecules withinthe film, with the alignment being better the thinner the film; onlyafter this orientation does the film exhibit an interference colour.Owing to the monomer architecture of the molecules of theliquid-crystalline polymers, equal interplanar spacings areautomatically established as, consequently, are diffraction structureshaving a colour-selective effect, in the shearing process in the courseof knife-coating.

The effective interference colour of the pigments, which are transparentand colourless per se, can be formed by adapting, in the smectic orcholesteric phases of the interference pigments, the equidistantlyspaced planes, in terms of their interplanar spacings, to the wavelengthof a particular coloration of the colour-defining coating layer, whichcan be achieved by suitable chemical structuring measures in respect ofthe molecular architecture. The Applicant has been able to prepareinterference pigments having the basic colour red and others with thebasic colour green. Advantageously it is possible to produceintermediate colours by mixing different interference pigments,together, into a base coating material, the colouring depending on themixing ratio of the different interference pigments. Since this mixingratio is infinitely variable, it is also possible to set, infinitely,all colour graduations for the basic shade

The basic shade of the interference pigments is determined by theperceived colour, or the colour which is established when the paintedsurface is viewed perpendicularly under perpendicular illumination.Since, with a beam path directed diagonally to the surface, theinterplanar spacings as a result of geometry--appear altered relative tothe orthogonal beam direction, the perceived colour shifts towards adifferent colour, which in the colour spectrum is displaced in thedirection of shorter wavelengths, depending on the relative direction ofviewing of the surface. In other words, depending on the position of acertain part of the surface relative to the beam path of the viewer,that part of the surface appears in the basic colour or in thedifferent, shorter-wave colour. Interference pigments of basic colourred, for example, can "flip" into the colour green; with otherinterference pigments, a flip in colour ("colour flop") between greenand blue can be produced.

The intensity of the colours which can be perceived in this context isall the greater the darker the colour of the substrate which carries thecolour-defining coating layer, although the shade of this substrate mustbe determined by colour pigments having an absorptive effect. The basisfor this, in fact, is that the light fractions passing through theinterference pigments are absorbed more or less completely by the darksubstrate, and are absorbed all the more the darker the substrate. Thelighter (in colour) the substrate, the greater the light fraction of thenon-interfering light which is likewise reflected back from thesubstrate and is superimposed on the fraction of light thrown back bythe interference pigments, so that the colour intensity of the latterappears paler. The lighter, therefore, the substrate, the lower thecolour intensities of the basic colour. This goes so far that, onchromium-plated bright components, for example, it is absolutelyimpossible to achieve any colour effect, since on a mirror-likesubstrate there is no spectral shift in intensity in the light.

One condition for the occurrence of liquid-crystalline phases is a rigidmesogenic molecular structure. The repeating units of liquid-crystallinepolymers comprise the mesogenic units. The two most frequently realizedmolecular structures are the side-chain LC polymers, in which themesogenic units are chemically fixed as side chains on the polymerbackbone, and the main-chain LC polymers, in which the mesogenic unitsform the polymer backbone, or part of the polymer backbone. In additionto the homopolymers, it is possible to prepare a large number ofcopolymers which may contain different mesogenic units, or mesogenic andnonmesogenic units.

SUMMARY OF THE INVENTION

EP 358 208 A2 describes liquid-crystalline organosiloxanes and theirpreparation, which contain (meth)acryloxy groups and which can beemployed, inter alia, as pigments in paints. According to the reportedexample, the liquid-crystalline polymers are formed from a low molarmass nematic component, containing methacrylic groups, and of a lowmolar mass chiral compound, which are crosslinked. From this document,however, it is not possible to obtain any indications of howinterference pigments can be produced by selecting an optimizedcomposition of materials which has improved colour brightness.

WO 91/13125 describes pigments for paints, where plateletlike substratesare coated with one or more metal oxides, the coating comprising achiral, irridescent liquid-crystalline medium. In accordance with theexamples cited therein, the liquid-crystalline compositions consist oflow molar mass chiral and nematic, P-pentyl-based and/orcholesteryl-based compounds. These classes of compounds are unsuitablefor the present application case of weather-resistant and mechanicallyresistant coating systems.

GB 2 132 623 A discloses liquid-crystalline polymers which are obtainedfrom low molar mass chiral cholesterol derivatives. The polymer filmsexhibit irridescent properties. The addition of low molar mass nematiccompounds, which also include photopolymerizable groups (e.g.4-methoxyphenyl 4- 6-methacryloyloxyhexyl-oxy!benzoate) is proposed.This document too, however, does not reveal any indications ofinterference pigments of the composition which is relevant or ofinterest in the present case.

The object of the invention, in relation to the various categories takenas the basis for the generic types, namely interference pigments,process for their preparation, coating material and coating systemapplied on a commodity article, is to find a material base which isindependent of the base of the polysiloxanes and, in effect coatingmaterials and effect coatings, gives rise to an improved brightness inthe perceived colour, it being intended that the interference pigmentused should possess an improved chemical and physical compatibility withthe customary paint vehicles and should also be able to be prepared in atechnically simple manner at favourable cost.

This object is achieved in accordance with the invention by interferencepigments comprising liquid side chain mesogens with nematic, smectic orcholesteric orders. It is also achieved with a process for theirpreparation, a coating system and an applied coating system.

It is known that liquid-crystalline polymers, owing to their highmolecular weight and the resulting high viscosity, possess a longorientation time. This disadvantage is avoided in accordance with theclaims by the use of low molar mass mono- or difunctional acrylates,methacrylates, epoxides or vinyl ethers, which have a considerablyshorter orientation time and can be crosslinked in order to "freeze in"the mesophase formed. The polymeric networks obtained in this way nolonger exhibit any liquid-crystalline transitions, and until thermaldecomposition they remain in a highly ordered state which is conserved.The coloured films and/or the interference pigments are obtained byadmixing a low molar mass chiral compound to the nematic component,thereby inducing the formation of the chiral-nematic reflecting phase.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this context it has been found in practice, in the course of thepreparation of the colour-imparting films and/or of the pigments, thatit is preferable to employ chiral compounds possessing goodliquid-crystalline properties and good crosslinking properties. If acholesteric network is prepared with nonmesogenic diacrylates, acrosslinking agent is added, for example a 1,4-diacryloyloxybenzene.

Some of the nematic and chiral components employed are available ascommercial products, and/or their preparation is known from theliterature. The preparation of the nematic component 1,4-diphenyl di4-(6-acryloyloxyhexyloxy)benzoate! is described by D. J. Broer; J.Boven; G. N. Mol; G. Challa; Makromol. Chem. 190, 2255 (1989) and thepreparation of the nematic component 4'-methoxybiphenyl4-(8-acryloyloxy-3,6-dioxyoctoyloxy)benzoate has been carried out by M.Engel; B. Hisgen; R. Keller; W. Kreuder; B. Reck; H. Ringsdorf; H.-W.Schmidt; P. Tschirner; Pure and Appl. Chem. 57 (1985) 1009.

2-Octyl 4-(4-hexyloxybenzoyloxy)benzoate is marketed as a commercialproduct by the company Merck under the designation S 811. The chiralcomponent cholesteryl butyrate is marketed by the company Fluka underorder number 26 770. The preparation of the chiral component cholesterylacrylate employed is described by A. C. De Visser; K. De Groot; J.Feyen; A. Brantjes; J. Polym. Sci., A-1, 9, 1893 (1971). The preparationof the chiral component cholesteryl 4-(6-acryloyloxyhexyloxy)benzoatewas carried out by esterification with cholesterol via the correspondingacid chloride. The 1,4-diacryloyloxybenzene employed as crosslinkingagent was prepared in accordance with L. Liebert; L. Strzelecki; D.Vagogne; Bull. Soc. Chim. Fr. 9-10, 2073 (1975).

The film produced in connection with the preparation of the interferencepigments should at least after curing have a thickness of from 3 to 15μm. In the case of thinner films, the desired interference-effectivecolour phenomenon is lost, and, in the case of thicker films, thealignment of the molecules is not as good, so that the colour phenomenonis impaired by a milky appearance. By breaking down the cured film insmall particles, the interference pigments required in the present caseare produced in platelet form, in which likewise, or as before, theside-group mesogens are in at least approximately nematic and/or smecticand/or, preferably, cholesteric order. The plateletlike interferencepigments which can be used have a platelet diameter in the order of from5 to 100 μm, or approximately from one to ten times the film thickness;larger or smaller particles produced during comminution of the fullycured film must be systematically removed, for example by sievingoperations. When the basecoat pigmented with them is applied to asurface, the plateletlike pigments automatically arrange themselvesparallel to the surface as a result of shear forces in the basecoat. Thesmall particles, which tend to approximate to the cubic form, do not,however, align themselves in the applied coating material parallel tothe surface of the component, which is why they should be systematicallyremoved. The very large pigment platelets may give rise to problemsduring application of the coating material, which is why pigments ofsuch a size should also be removed by sieving.

Another expedient embodiment of the coating system can be seen inkeeping the substrate of the colour-defining coating layer in a shade,brought about by means of absorption pigments, which is such that itapproximately coincides with the basic colour or with the "flop" colourof the interference pigments. This gives the colour coincident with thesubstrate a particularly intense and brilliant appearance. Although inthe other viewing direction or illumination direction the colour of thecoated surface also appears in the respective substrate shade, it istinted in the other colour of the interference pigments and is strewnwith finely dispersed points of sparkle. In addition, it is of coursealso possible, using absorption pigments, to give the substrate carryingthe colour-defining coating layer neither a dark shade nor a shade inone of the colours of the interference pigments but in a third shade,which for example is in the colour spectrum between both colours or hasa particularly large spectral distance from at least one of the twocolours. In this way it is possible to give the coated article athree-way perceived colour.

As an alternative or else a supplement giving the substrate whichcarries the colour-defining coating layer a shading appropriate to itsuse, it is also conceivable to mix absorption pigments into the effectpaint containing--in some instances possibly different--interferencepigments. By admixing dark absorption pigments to the novel effect paintit is possible to obtain an impression wholly comparable with that givenby a dark substrate. The situation is similar when light-colouredabsorption pigments are mixed in; they bring about an attenuation of thecolour flop and of the individual colour intensities. By admixingabsorption pigments in one of the effect colours it is possible toachieve an intensification of this perceived colour at the expense ofthe colour effect of the other effect colour. The admixing of absorptionpigments to the effect paint is advisable if the intention is--forwhatever reason--to paint a light-coloured substrate, or even asubstrate having a metallic gleam, with effect paint. A task of thiskind may be required, for example, when repainting old vehicles or inthe course of refinish operations.

In the text below the invention is illustrated in more detail withreference to examples.

Production of the Colour-imparting Film

The polymer films are produced in an in situ photopolymerization in thecholesteric phase of the corresponding monomer mixture. A monomermixture consisting of 50 mol % of a nematic component and 50 mol % of achiral component, and also approximately 1% by weight of2,2-dimethoxy-2-phenylacetophenone, were dissolved in 1 ml ofchloroform. The nematic component used was a 1,4-diphenyl di4-(6-acryloyloxyhexyloxy)benzoate! and the chiral component used was acholesteryl acrylate. The reaction solution was applied to a substrate,for example to a film, to a metal plate or to a slide, with a coatingthickness of about 5 μm. After evaporating the solvent, the coatedsubstrate was heated to 115° C., at which point the mesophase was formedin the monomer mixture. Good orientation was obtained by knife-coatingthe reaction solution onto the substrate, treating it with electrical ormagnetic fields, or applying an alignment layer to the substratebeforehand. The applied film was subsequently cured by means of UVlight. The cured film, when viewed straight on under perpendicularillumination, had a violet colour.

By varying the content of the two components it is possible to establishreflection colours in the entire visible region of the spectrum and inthe IR range within the film, as is evident from the table below.

    ______________________________________                                        Proportion of chiral monomer                                                                    Reflection wavelength                                       (mol %)           λ.sub.R (nm)                                         ______________________________________                                        10                1668                                                        20                998.0                                                       30                674.5                                                       35                572.0                                                       40                512.5                                                       45                474.0                                                       50                435.5                                                       60                378.0                                                       70                362.5                                                       ______________________________________                                    

Preparation of the Interference Pigments

The colour-imparting film was scraped off from the substrate using ablade-like tool to give flake-like structures. The flakes weresubsequently comminuted with an air jet mill (from Alpine); it is alsopossible to employ other mills, incorporating gentle heating, forplastics parts. The resulting milled material was then sieved, and asieve fraction having a mean size of about 30 μm was used for furtherprocessing.

Preparation of the Paint

The interference pigments obtained were mixed with a clearcoat in aratio of from 1:7 to 1:20 parts by weight. The clearcoat used was atwo-component topcoat based on polyurethane; e.g. 2k-PU-decklack 0111from BASF Lacke und Farben or a "Standox" coating material fromHerberts.

Effect Finishing of a Bodywork Component

The effect paint was applied by a nematic spraying technique (equipment:SATA) to a vehicle sunroof cover which had been primed using a blackfiller coating, Applicant's designation DL 0404. An electrostaticapplication technique for the novel effect paint using high-speedrotating spraying bells appears to be another possibility. Followingapplication, the effect paint was first dried and then subjected toforce thermal curing.

The result obtained on the bodywork component was a coloured coatingwhich, under diffuse white light--with a cloudy sky--appeared in anintense violet coloration or in a green shade depending on the directionof viewing.

Another colour-imparting film was prepared from 1,4-di(2-methyl)phenyldi 4-(6-acryloyloxy)hexyloxy!benzoate as nematic component and2,3-cholesteryl (2-acryloyloxyethoxy)benzoate as chiral component. Thefilm was produced by the procedure indicated in the previous example,with the difference that the coated substrate was heated to 90° C.

For this film, the following reflection wavelengths were established:

    ______________________________________                                        Proportion of chiral monomer                                                                    Reflection wavelength                                       (mol %)           λ.sub.R (nm)                                         ______________________________________                                        10                1668                                                        20                998                                                         30                674                                                         35                572                                                         40                512                                                         45                474                                                         50                435                                                         60                378                                                         70                362                                                         ______________________________________                                    

The advantages achieved with the subject-matter of the inventionconsist, in particular, in that with the effect coating material and,respectively, with the effect coating system an even higher brightnessof colour, with a high degree of light stability, is achieved than itwas possible to obtain with the interference pigments known to date.This can be explained by the fact that the novel interference pigmentsdevelop very narrow-band absorption curves for the various colours.Moreover, the interference pigments possess improved chemical andphysical compatibility with the customary coating materials with whichthey are mixed. Relative to those known to date, the novel interferencepigments possess a substantially higher degree of crosslinking, which isachieved in particular when the difunctional nematic diacrylates anddifunctional chiral-nematic diacrylates are used. The interferencepigments prepared possess high mechanical stability and great colourstability, and exhibit outstanding adhesiveness and wettability. Thestarting components for the liquid-crystalline side-chain polymersmoreover, are simple and inexpensive to prepare.

We claim:
 1. Interference pigments for colored coating materialscomprising liquid-crystalline side-chain polymers, comprising side-chainmesogens having at least one of an nematic, smectic and cholestericorder, wherein:the liquid-crystalline side-chain polymers are formed bycrosslinking starting components, the starting components comprise anematic component and a chiral component, the nematic component isselected from the group of mono- and difunctional low molar masscompounds consisting of:1,4-diphenyl di4-(acryloyloxy)alkyloxy!benzoates, 1,4-di(2-methyl)phenyl di4-(acryloyloxy)alkyloxy!benzoates, 1,4-di(2-methoxy)phenyldi4-(acryloyloxy)alkyloxy!benzoates, and mixtures thereof, and the chiralcomponent is selected from the group of optically isomeric low molarmass compounds having a chiral center consisting of:3,5-cholesteryl(acryloyloxyalkoxy)benzoate, 3,4-cholesteryl(acryloyloxyalkoxy)benzoate, 2,5-cholesteryl(acryloyloxyalkoxy)benzoate, 2,4-cholesteryl(acryloyloxyalkoxy)benzoate,β-oestra-3,17-diyl(acryloylalkyloxy)benzoate, β-oestra-3,17-diylacrylate, R- or S-1,1'-bi-2-naphthoyl4-alkoxybenzoyloxy!(4,4-biphenyloyloxyalkoxyacrylate), R- orS-1,1'-bi-2-naphthoylhexylterephthaloyl!(4,4-biphenyloyloxyalkoxyacrylate),
 1. 4-diphenyl R-or S-di 4-(3-acryloyloxy-2-methylpropoxy)benzoate!,2-octyl4-(4-hexyloxybenzoyloxy!benzoate, 1,4-dyphenyl di4-(3-acryloyloxy-2-methylpropoxy!benzoate, 1,4-di(2-methyl)phenyl di4-(3-acryloyloxy-2-methyl-propoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(3-acryloyloxy-2-methyl-propoxy!benzoate, 1,4-diphenyl di4-(1-acryloyloxy-1-methylethoxy!benzoate, 1,4-di (2-methyl)phenyl di4-(1-acryloyloxy-1-methyl-ethoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(1-acryloyloxy-1-methyl-ethoxy!benzoate, 1,4-diphenyl di4-(6-acryloyloxy-3-methylhexoxy!benzoate, 1,4-di(2-methyl)phenyldi4-(6-acryloyloxy-3-methylhexoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(6-acryloyloxy-3-methyl-hexoxy!benzoate, and mixtures thereof.
 2. Theinterference pigments according to claim 1, wherein a crosslinking agentconsisting of 1,4-diacryloyloxybenzene is added to the startingcomponents.
 3. The interference pigments according to claim 1, whereinthe interference pigments have a thickness of from about 3 to 15 μm. 4.The interference pigments according to claim 1, wherein the interferencepigments are platelet-like and have a diameter of from 5 to 100 μm. 5.The interference pigments according to claim 1, wherein the interferencepigments are platelet-like and have a diameter of from 10 to 50 μm.
 6. Aprocess for the preparation of platelet-like interference pigmentscomprising:producing a film of molecules having at least one of annematic, smectic and cholesteric order by applying liquid-crystallineside-chain polymers in a liquid state to a smooth substrate, curing thefilm, removing the cured film from the substrate, comminuting the curedfilm into platelet-like particles, and separating out particles having adiameter smaller than the film thickness and particles having a diameterwhich is more than ten times the film thickness by a particlesize-selective separation process before subsequently processing theremaining particles as interference pigments,wherein the film ofliquid-crystalline side-chain polymers is applied as a solventapplication or melted powder, whereinthe liquid-crystalline side-chainpolymers are formed by crosslinking starting components, the startingcomponents comprise a nematic component and a chiral component, thenematic component is selected from the group of mono- and difunctionallow molar mass compounds consisting of:
 1. 4-diphenyl di4-(acryloyloxy)alkyloxy!benzoates,1,4-di(2-methyl)phenyl di4-(acryloyloxy)alkyloxy!-benzoates, 1,4-di(2-methoxy)phenyl di4-(acryloyloxy)alkyloxy!-benzoates, and mixtures thereof, and the chiralcomponent is selected from the group of optically isomeric low molarmass compounds having a chiral center consisting of:3,5-cholesteryl(acryloyloxyalkoxy)benzoate,
 3. 4-cholesteryl(acryloyloxyalkoxy)benzoate,2,5-cholesteryl (acryloyloxyalkoxy)benzoate,2,4-cholesteryl (acryloyloxyalkoxy)benzoate, β-oestra-3,17-diyl(acryloyloxyalkoxy)benzoate, β-oestra-3,17-diyl acrylate, R- orS-1,1'-bi-2-naphthoyl4-alkoxybenzoyloxy-(4,4-biphenyloyloxyalkoxyacrylate), R- orS-1,1'-bi-2-naphthoylhexylterephthaloyl!-(4,4-biphenyloyloxyalkoxyacrylate), 1,4-diphenyl R-or S-di 4-(3-acryloyloxy-2-methyl-propoxy)benzoate!, 2-octyl4-(4-hexyloxybenzoyloxy!benzoate, 1,4-diphenyl di4-(3-acryloyloxy-2-methylpropoxy!-benzoate, 1,4-di(2-methyl)phenyl di4-(3-acryloyloxy-2-methylpropoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(3-acryloyloxy-2-metholpropoxy!benzoate, 1,4-diphenyl di4-(1-acryloyloxy-1-methylethoxy!benzoate, 1,4-di(2-methyl)phenyl di4-(1-acryloyloxy-1-methyl-ethoxy!benzoate, 1,4-di(2-methoxy)phenyl di4(1-acryloyloxy-1-methylethoxy!benzoate,
 1. 4-diphenyl di4-(6-acryloyloxy-3-methylhexoxy!benzoate,1,4-di(2-methyl)phenyl di4-(6-acryloyloxy-3-methylhexoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(6-acryloyloxy-3-methylhexoxy!benzoate, and mixtures thereof.
 7. Theprocess according to claim 6, comprising adding a crosslinking agentconsisting of 1,4-diacryloyloxybenzene to the starting components. 8.The process according to claim 6, comprising knife-coating the film tothe substrate in a thickness of from about 3 to 15 μm.
 9. The processaccording to claim 6, comprising processing particles having a diameterof from 5 μm to 100 μm as interference pigments.
 10. The processaccording to claim 6, comprising processing particles having a diameterof from 10 to 50 μm as interference pigments.
 11. A coating material forpainting articles comprising interference pigments which areincorporated by mixing, wherein at least some of the interferencepigments are platelet-like and automatically align themselvesapproximately parallel to the surface of the article during applicationof the coating material, and are composed of liquid-crystallineside-chain polymers, comprising side-chain mesogens have at least one ofan nematic, smectic and cholesteric order, wherein:theliquid-crystalline side-chain polymers are formed by crosslinkingstarting components, the starting components comprise a nematiccomponent and a chiral component, the nematic component is selected fromthe group of mono- and difunctional low molar mass compounds consistingof:1,4-diphenyl di 4-(acryloyloxy)alkyloxy!benzoates,1,4-di(2-methyl)phenyl di 4-(acryloyloxy)alkyloxy!benzoates,1,4-di(2-methoxy)phenyl di 4-(acryloyloxy)alkyloxy!benzoates, andmixtures thereof, and the chiral component is selected from the group ofoptically isomeric low molar mass compounds having a chiral centerconsisting of:3,5-cholesteryl (acryloyloxyalkoxy)benzoate,3,4-cholesteryl (acryloyloxyalkoxy)benzoate, 2,5-cholesteryl(acryloyloxyalkoxy)benzoate, 2,4-cholesteryl(acryloyloxyalkoxy)benzoate, β-oestra-3,17-diyl(acryloyloxyalkoxy)benzoate, β-oestra-3,17-diyl acrylate, R- orS-1,1'-bi-2-naphthoyl4-alkoxybenzoyloxy!(4,4-biphenyloyloxyalkoxyacrylate), R- orS-1,1'-bi-2-naphthoylhexylterephthaloyl!(4,4-biphenyloyloxyalkoxyacrylate),
 1. 4-diphenyl R-or S-di 4-(3-acryloyloxy-2-methylpropoxy)benzoate!,2-octyl4-(4-hexyloxybenzoyloxy!benzoate, 1,4-diphenyl di4-(3-acryloyloxy-2-methylpropoxy!benzoate, 1,4-di(2-methyl)phenyl di4-(3-acryloyloxy-2-methylpropoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(3-acryloyloxy-2-methylpropoxy!benzoate, 1,4-diphenyl di4-(1-acryloyloxy-1-methylethoxy!benzoate, 1,4-di(2-methyl)phenyl di4-(1-acryloyloxy-1-methylethoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(1-acryloyloxy-1-methylethoxy!benzoate, 1,4-diphenyl di4-(6-acryloyloxy-3-methylhexoxy!benzoate, 1,4-di(2-methyl)phenyl di4-(6-acryloyloxy-3-methylhexoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(6-acryloyloxy-3-methylhexoxy!benzoate, and mixtures thereof.
 12. Thecoating material according to claim 11, wherein all the interferencepigments are platelet-like.
 13. Coating material according to claim 11,wherein a crosslinking agent consisting of 1,4-diacryloyloxybenzene isadded to the starting components.
 14. The coating material according toclaim 11, wherein the interference pigments having different interplanarspacings are present and mixed in the coating material.
 15. The coatingmaterial according to claim 11, wherein the interference pigments have athickness from about 3 to 15 μm.
 16. The coating material according toclaim 11, wherein the platelet-like interference pigments have adiameter of from 5 to 100 μm.
 17. The coating material according toclaim 11, wherein the platelet-like interference pigments have adiameter of from 10 to 50 μm.
 18. A vehicle body painted with a coatingmaterial according to claim
 11. 19. A coating system for application toan article to define the color of the article, comprising acolor-defining coating layer comprising pigments, wherein at least someof the pigments are interference pigments, wherein depending on thedesired color of the article, the interference pigments areplatelet-like and align themselves approximately parallel to the surfaceof the article and consist of crosslinked liquid-crystalline side-chainpolymers, comprising side-group mesogens having at least one of annematic, smectic and cholesteric order, wherein:the liquid-crystallineside-chain polymers are formed by crosslinking starting components, thestarting components comprise a nematic component and a chiral component,the nematic component is selected from the group of mono- anddifunctional low molar mass compounds consisting of:1,4-diphenyl di4-(acryloyloxy)alkyloxy!benzoates, 1,4-di(2-methyl)phenyl di4-(acryloyloxy)alkyloxy!benzoates, 1,4-di(2-methoxy)phenyldi4-(acryloyloxy) alkyloxy!benzoates, and mixtures thereof, and the chiralcomponent is selected from the group of optically isomeric low molarmass compounds having a chiral center consisting of:3,5-cholesteryl(acryloyloxyalkoxy) benzoate, 3,4-cholesteryl (acryloyloxyalkoxy)benzoate, 2,5-cholesteryl (acryloyloxyalkoxy)benzoate, 2,4-cholesteryl(acryloyloxyalkoxy) benzoate, β-oestra-3,17-diyl(acryloyloxyalkoxy)benzoate, β-oestra-3,17-diyl acrylate, R- orS-1,1'-bi-2-naphthoyl4-alkoxybenzoyloxy!(4,4-biphenyloyloxyalkoxyacrylate), R- orS-1,1'-bi-2-naphthoylhexylterephthaloyl!(4,4-biphenyloyloxyalkoxyacrylate), 1,4-diphenyl R-or S-di 4-(3-acryloyloxy-2-methylpropoxy)benzoate!, 2-octyl4-(4-hexyloxybenzoyloxy!benzoate, 1,4-diphenyl di4-(3-acryloyloxy-2-methylpropoxy!benzoate, 1,4-di(2-methyl)phenyl di4-(3-acryloyloxy-2-methylpropoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(3-acryloyloxy-2-methylpropoxy!benzoate, 1,4-diphenyl di4-(1-acryloyloxy-1-methylethoxy!benzoate, 1,4-di(2-methyl)phenyl di4-(1-acryloyloxy-1-methylethoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(1-acryloyloxy-1-methylethoxy!benzoate,
 1. 4-diphenyl di4-(6-acryloyloxy-3-methylhexoxy!-benzoate,1,4-di(2-methyl)phenyl di4-(6-acryloyloxy-3-methylhexoxy!benzoate, 1,4-di(2-methoxy)phenyl di4-(6-acryloyloxy-3-methylhexoxy!benzoate, and mixtures thereof.
 20. Thecoating system according to claim 19, wherein all the pigments areinterference pigments.
 21. The coating system according to claim 19,wherein a crosslinking agent consisting of 1,4-diacryloyloxybenzene isadded to the starting components.
 22. The coating system according toclaim 19, wherein the color-defining coating layer comprising theinterference pigments is applied to a dark colored substrate.
 23. Thecoating system according to claim 19, wherein the color-defining coatinglayer comprising the interference pigments has at least two shades andis applied to a substrate having the same color as one shade of thecolor-defining coating layer.
 24. The coating system according to claim19, wherein interference pigments having different interplanar spacingsare present and mixed in the color-defining coating layer.
 25. Thecoating system according to claim 19, wherein the interference pigmentshave a thickness of from about 3 to 15 μm.
 26. The coating systemsaccording to claim 19, wherein the platelet-like interference pigmentshave a diameter of from about 5 to 100 μm.
 27. The coating systemsaccording to claim 19, wherein the platelet-like interference pigmentshave a diameter of from about 10 to 50 μm.
 28. A vehicle body paintedwith a coating system according to claim 19.